Stopping you right there. You're aware you're talking about Doctor Who, right? This is practically Continuity Problems: The Series. Basically, everything is only loosely canon.

Case in point: The Daleks. Their very first story gave them an origin of nuclear-mutants from an ancient race called Dals, who were eternally at war with the Thals. Then "Genesis of the Daleks" changed it up by showing a new origin at the hands of Davros. Still at war with the Thals, the race was now called the "Kaled" race, and Davros almost single-handedly created them as purposeful genetic mutants bred for superiority and survival, each with their own transportable tank. So they were no longer peaceful scientists turned savage while the militant savages turned peaceful. The Daleks just became the brainchild of a madman.

Item Two! The Brain of Morbius. Featured is a segment where we see many faces unknown to us. These were intended to be the faces of the Doctor prior to the First Doctor. This is now discontinuity.

Item Three! The Eighth Doctor TV Movie, sometimes called "The Enemy Within." The Doctor claims to be half-human. As of NuWho, this is pretty much disregarded, though McGann is still credited as the Eighth Doctor.

Item Four! Two accounts of the destruction of Atlantis. I believe one was in the Second Doctor's run, and the other was in the Third Doctor's run, but I'd have to check that.

Also, the Daleks have gone extinct more times than one could ever count. There is no "Very Final End" for them. Or the Master. Or the Cybermen, even after they lost their homeworld in the very first story in which they appear. Cybermen also seem to change their appearance a lot. And their weaknesses.

Item Five! Regeneration count. I believe this was initially brought for a story involving the Master running out and trying to get more. Now it's pretty much shrugged off. This could be due to the Time War and its results, however, as they generally keep up with the rule after this came up (though it was never mentioned beforehand).

Should I go on, or can we pretty much agree now that there is no continuity in Doctor Who beyond what the writers feel like accepting that week?

The series wouldn't of lasted this long if not for the plot holes and loopholes.

How do you continue the series? Make the Doctor regenerate (which came about in the first place because Hartnell's health was failing and they didn't want to stop the show). It also says that the Doctor can't cross paths with himself and yet there are many episodes where the Doctor meets his past selves.

We just have to remember that time is just a ball of wibbly-wobbly timey-wimey stuff. If we try to over think it, our heads will explode.

I've never seen that Christmas special so I wouldn't know what to say on that, although I've also spotted a few continuity issues as well. Of the top of my head is Cassandra. When we see her first in episode 2 of season one she says that she is the last true human left and this was five billion years into Rose's future yet when the 10th doctor travels to the year one trillion or some thing, we see humans in their basic form. It threw me off for a bit but then I just shrugged it off and continued to watch the episode.

First off, she said she was the last "true" human, meaning she was the last pure human. There were others that still looked human but might have been slightly different. No one seemed to question The Doctor and Rose's appearance as humans.

Second, in the episode New Earth (which took place 15 years after her first episode), a whole new race of pure humans is unleashed when all the sick guinea pig people are cured.

Third, in the episode where they go to the end of the universe, The Doctor says that no matter how much the human race changes, they always revert back to this basic form.

Fourth, This is Doctor Who, it has too long of a history for them to not f**k with continuity every now an then.

The Doctor's half-human himself right? I remember them driving that point home again and again in the TV movie. Anyway....as far as continuity in Who? Say it with me everyone! All together now!

I only got to see A Christmas Carol yesterday and the same question bothered me.
I'm glad I came upon this thread, at least I was enlightened a bit and came upon the conclusion
(just like you did, I suppose) that time is a wibbly wobbley timey wimey stuff. Very clear, thanks. :)

I only got to see A Christmas Carol yesterday and the same question bothered me.
I'm glad I came upon this thread, at least I was enlightened a bit and came upon the conclusion
(just like you did, I suppose) that time is a wibbly wobbley timey wimey stuff. Very clear, thanks. :)

In the season 1 episode, Father's Day, time was ALREADY unstable because Rose had changed the past by saving her father, Pete, from dying.
As the Doctor says, time can be rewritten, but not everything can be. Turns out, Pete's death was a fixed point in time. So by saving him, Rose had caused a paradox, a "wound in time". The Reapers were released and started eating people in this "wound in time" in an attempt to seal it before major damage to the universe could be done. Or something.
The Doctor got Rose, Jackie, baby Rose, Pete, and all the people nearby into a church on the street. His reasoning was that, because the church was so old, that the Reapers couldn't get in? I'm not clear on that bit. But anyway, he warns Rose not to let herself touch her past self, because that would cause ANOTHER paradox (possibly one that would be even worse, because it occurred when time was already messed up), and thus ruin the protection that the old church gave them and let the Reapers in.

Anyway! In A Christmas Carol, the Doctor changes small things about Kazran's past, but nothing important, and nothing that was a fixed point. It's possible that the universe not already being out of whack like it was in Father's Day could be part of the reason that Past Kazran and Future Kazran touching didn't have disastrous consequences.

Yay for speculation~

Also, in A Christmas Carol, he wasn't exactly crossing his own timeline, not in the same way as in Father's Day. Nice Kazran or mean Kazran, the ship Amy and Rory were on would still be crashing, so The Doctor would still have the need to visit Kazran. So, he could still technically go into the past without necessarily crossing his timestream. Also, in Father's Day there were two of the same Doctor, which throws things out of whack much more than the Doctor simply changing someone's history.